/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.trace;

import org.apache.hadoop.conf.Configuration;
import org.apache.htrace.core.HTraceConfiguration;
import org.apache.htrace.core.Sampler;
import org.apache.htrace.core.Span;
import org.apache.htrace.core.SpanReceiver;
import org.apache.htrace.core.TraceScope;
import org.apache.htrace.core.Tracer;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * This wrapper class provides functions for accessing htrace 4+ functionality in a simplified way.
 */
@InterfaceAudience.Private
public final class TraceUtil {
    private static HTraceConfiguration conf;
    private static Tracer tracer;

    private TraceUtil() {
    }

    public static void initTracer(Configuration c) {
        if(c != null) {
            conf = new HBaseHTraceConfiguration(c);
        }

        if(tracer == null && conf != null) {
            tracer = new Tracer.Builder("Tracer").conf(conf).build();
        }
    }

    /**
     * Wrapper method to create new TraceScope with the given description
     * @return TraceScope or null when not tracing
     */
    public static TraceScope createTrace(String description) {
        return (tracer == null) ? null : tracer.newScope(description);
    }

    /**
     * Wrapper method to create new child TraceScope with the given description
     * and parent scope's spanId
     * @param span parent span
     * @return TraceScope or null when not tracing
     */
    public static TraceScope createTrace(String description, Span span) {
        if(span == null) {
            return createTrace(description);
        }

        return (tracer == null) ? null : tracer.newScope(description, span.getSpanId());
    }

    /**
     * Wrapper method to add new sampler to the default tracer
     * @return true if added, false if it was already added
     */
    public static boolean addSampler(Sampler sampler) {
        if(sampler == null) {
            return false;
        }

        return (tracer == null) ? false : tracer.addSampler(sampler);
    }

    /**
     * Wrapper method to add key-value pair to TraceInfo of actual span
     */
    public static void addKVAnnotation(String key, String value) {
        Span span = Tracer.getCurrentSpan();
        if(span != null) {
            span.addKVAnnotation(key, value);
        }
    }

    /**
     * Wrapper method to add receiver to actual tracerpool
     * @return true if successfull, false if it was already added
     */
    public static boolean addReceiver(SpanReceiver rcvr) {
        return (tracer == null) ? false : tracer.getTracerPool().addReceiver(rcvr);
    }

    /**
     * Wrapper method to remove receiver from actual tracerpool
     * @return true if removed, false if doesn't exist
     */
    public static boolean removeReceiver(SpanReceiver rcvr) {
        return (tracer == null) ? false : tracer.getTracerPool().removeReceiver(rcvr);
    }

    /**
     * Wrapper method to add timeline annotiation to current span with given message
     */
    public static void addTimelineAnnotation(String msg) {
        Span span = Tracer.getCurrentSpan();
        if(span != null) {
            span.addTimelineAnnotation(msg);
        }
    }

    /**
     * Wrap runnable with current tracer and description
     * @param runnable to wrap
     * @return wrapped runnable or original runnable when not tracing
     */
    public static Runnable wrap(Runnable runnable, String description) {
        return (tracer == null) ? runnable : tracer.wrap(runnable, description);
    }
}
